This project hasn't been updated in 8 years. I'm not sure if it even works right now.
There is a currently maintained and actively developed project for the same purpose over here: https://mishcatt.github.io/VTF-Editor
And the github repo for it here: https://github.com/Mishcatt/VTF-Editor
A front end to vtex (source SDK tool) to: -create fading sprays using mipmap levels -create animated sprays from animated gifs
Written in python 2.x